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Inspection Procedure

NOTE: Read freeze frame data using the hand-held tester or the OBD II scan tool. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.
  1. CHECK OTHER DTCS OUTPUT (IN ADDITION TO DTC P0420) 
    1. Connect the hand-held tester or the OBD II scan tool to the DLC3.
    2. Turn the ignition switch ON and push the hand-held tester or the OBD II scan tool main switch ON.
    3. Select the item "DIAGNOSIS / OBD/MOBD / DTC INFO / CURRENT CODES".
    4. Read the DTCs using the hand-held tester or the OBD II scan tool.

      Result: 

      DTCS OUTPUT

      Display (DTC Output) Proceed To
      Only "P0420" Is Output A
      "P0420" And Other DTCs Are Output B
      NOTE: If any other codes besides "P0420" are output, perform the troubleshooting for those DTCs first.
    1. B : GO TO RELEVANT DTC CHART (See  DIAGNOSTIC TROUBLE CODE CHART  ) 
    2. A : Go to next step. 
  2. CHECK FOR EXHAUST GAS LEAKAGE 
    1. NG : REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT (See  REMOVAL & INSTALLATION AND DISASSEMBLY & REASSEMBLY  ) 
    2. OK : Go to next step. 
  3. INSPECT HEATED OXYGEN SENSOR (BANK 1 SENSOR 1) (See  DTC CHECK/CLEAR  6) 

    Refer to the hint below.

    1. NG : REPLACE HEATED OXYGEN SENSOR 
    2. OK : Go to next step. 
  4. INSPECT HEATED OXYGEN SENSOR (BANK 1 SENSOR 2) (See  DTC P0136 OXYGEN SENSOR CIRCUIT MALFUNCTION (BANK 1 SENSOR 2)  ) 

    Refer to the hint below.

    1. NG : REPLACE HEATED OXYGEN SENSOR 
    2. OK : REPLACE THREE-WAY CATALYTIC CONVERTER (EXHAUST MANIFOLD) 
NOTE: Hand-held tester only:

The following procedure enables the technician to identify a trouble area if malfunction in both front and rear heated oxygen sensors other than the catalyst converter, or the malfunction that indicates the actual air-fuel ratio extremely RICH or LEAN.

  1. Perform ACTIVE TEST using the hand-held tester (A/F CONTROL).
    NOTE: "A/F CONTROL" is ACTIVE TEST which changes the injection volume -12.5 % or +25 %.
    1. Connect the hand-held tester to the DLC3 on the vehicle.
    2. Turn the ignition switch ON.
    3. Warm up the engine by running the engine at 2,500 rpm for approximately 3 minutes.
    4. Select the item "DIAGNOSIS/ENHANCED OBD II/ACTIVE TEST/ A/F CONTROL".
    5. Perform "A/F CONTROL" with the engine in an idle condition (press the right or left button).

      Result: 

      Heated oxygen sensor reacts in accordance with increase and decrease of injection volume: 

      +25 % --> rich output: More than 0.55 V 

      -12.5 % --> lean output: Less than 0.4 V 

    NOTE: There is a delay of few seconds in the sensor 1 (front sensor) output, and there is about 20 seconds delay at maximum in the sensor 2 (rear sensor).
    Fig 1: Heated Oxygen Sensor Injection Volume
    G03367139Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

    The following A/F CONTROL procedure enables the technician to check and graph the voltage outputs of both the heated oxygen sensors.

    For displaying the graph indication, enter "ACTIVE TEST / A/F CONTROL / USER DATA", then select "O2S B1S1 and O2S B1S2" by pressing "YES" button and push "ENTER" button before pressing "F4" button.

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